The influcnce of host physiology on type C RNA virus expression and their participation in tumorigenesis is being examined. A rapid and sensitive assay for detecting and quantitating small differences in host cell X virus interaction, complemented by immunological and hormonal manipulation of virus expression in vivo are being used as a model system to comprehensively examine physiologic and other factors influencing viral carcinogenesis. BIBLIOGRAPHIC REFERENCES: Hellman, A., Fowler, A. K., Strickland, J. E., and Kouttab, N. M.: Type-C Virus Modulation by Estrogens: Its Possible Biological Function. In Deutsch, E., Moser, K., Rainer, H., and Stacher, A. (Eds.): Molecular Base of Malignancy. Stuttgart, Georg Thieme Verlag, 1976, pp. 206-216. Folwer, A. K., Strickland, J. E., Kouttab, N. M., and Hellman, A.: RNA tumor virus expression in mouse uterine tissue during pregnancy. Biol. Reprod. 16: 344-348, 1977.